We have recently provided the first evidence for the induction of protective immune response to simian immunodeficiency virus (SIV) in the genital tract of female rhesus macaques. We observed that systemic priming followed by oral or intratracheal boosting with a microencapsulated whole SIV vaccine induced SIV-specific secretory IgA responses in the vagina, and that significant protection was observed against intravaginal challenge with live pathogenic SIV. These results provide the basis for further exploring alternative approaches to develop improved vaccines for mucosal immunization against HIV. In this project a major goal is the production and characterization of non-infectious particulate antigens expressed by recombinant expression vectors, which should be particularly well suited for microencapsulation. Our initial focus will be on the gag and env genes of the infectious pathogenic molecular clone SIVmac239. We have already constructed a series of baculovirus recombinants and vaccinia virus recombinants expressing the SIV envelop and core proteins and we are investigating conditions for the production and purification of virus-like particles. Alternative cell lines and expression vectors are being employed to obtain particles which contain optimal amounts of envelope proteins. The VLP's will be provided to other injects for microencapsulation and, for evaluation in primates. In addition we will explore a novel approach for mucosal immunization which may have specific advantages including increased duration of the protective immune response. The recent discovery that intramuscular injection of plasmid DNA results in the expression of encoded proteins, and that this approach can be used for protective immunization against viral diseases, provides an attractive approach for induction of long term mucosal immune response. We will construct plasmid vectors encoding SIV and HIV antigens, and investigate the immune responses in mice after immunization by various mucosal routes. We will also explore the potential of alternate delivery systems for enhancing the immune to mucosally administered DNA constructs.